Populus I 83 1 



scarcely to be distinguished in technical characters from P. robusta, which is stami- 

 nate and bears considerably larger leaves, known from young trees only. P. robusta 

 appears to differ, however, in the grey and not yellowish colour of the branchlets 

 in their second year. /^ j^ \ 



The only large trees which we have seen of this are at Leaton Knolls, 

 Shrewsbury, the residence of Major Lloyd, who has no record of their origin or 

 date of planting. The largest, which is growing on a hill at the edge of an old 

 pit-hole, now dry, was 120 ft. by 13I ft. in July 19 10. The second tree is no ft. by 

 II ft. 2 in., and the third is 95 ft. by \o\ ft., as measured by myself in July and by 

 Major Lloyd in September 1910. None of the down lying on the ground in July 

 contained good seed as far as I could see. The trees are clearly of the same age 

 —possibly sixty or seventy years— and being all females, perhaps originated from 

 cuttings of a tree which may have existed in the neighbourhood, where P. nigra is 

 not uncommon. 



This hybrid may possibly in some cases have been hitherto confused by botanists 

 with P. nigra, var. betulifolia ; but it is apparently rare. The only other specimen 

 which we have seen is a tree ^ in a garden near Turnham Green Station, which is 

 about 35 feet high. It produced numerous natural seedlings in 1907, ten of which 

 were transplanted into the nursery at Kew, and were in 19 12 vigorous plants 

 2 to 3| ft. high. (H. J. E.) 



POPULUS ANGUSTIFOLIA 



Populus angustifolia, James, Lon^s Expedition, i. 497 (1823); Sargent, Silva N. Amer. ix. 171, t. 

 492 (1896), and Trees N. Amer. 159 (1905); ^c\m.€\Ae.x, Laubtwlzkunde, i. 14 (1904); Dode, in 

 Mem. Soc. Hist. Nat. Autun, xviii. 58 (1905) ; Gombocz, in Math. Termes. KM. xxx. 105 (191 1). 



Populus salicifolia, Rafinesque, Alsograph. Amer. 43 (1838) (not Loudon). 



Populus canadensis, Desfontaines, var. angustifolia, Wesmael, in De CandoUe, Prod. xvi. 2, 329 

 (1868). 



Populus balsamifera, Linnasus, var. angustifolia, Watson, Kin^s Rep. v. 327 (1871). 



Populus coloradensis, Dode, in MSm. Soc. Hist. Nat. Autun, xviii. 58 (1905). 



A tree, attaining in America 60 ft. in height and 5 ft. in girth. Bark smooth, 

 yellowish green, becoming fissured at the base of old trunks. Young branchlets 

 glabrous, rounded, yellowish grey. Buds minute, viscid, sharp -pointed. Leaves 

 (Plate 410, Fig. 26), lanceolate on long shoots, resembling those of Salix fragilis in 

 shape, about 2 to 4 in. long, f to i in. wide, cuneate at the base, gradually tapering 

 to a gland-tipped acute or rounded apex, glabrous, pale green and not whitish 

 beneath ; margin revolute, with close fine glandular serrations ; lateral nerves, about 

 fifteen pairs, all pinnate ; petiole short, glabrous, flattened above. On the short 

 shoots, the leaves become shorter and broader, almost rhombic in outline. 



Catkins densely flowered, glabrous ; scales obovate, with irregularly cut dark 

 brown filiform lobes. Stamens twelve to twenty in a cup-shaped slightly oblique 

 disc, with a thickened reflexed margin. Ovary two-lobed, with two stigmas, enclosed 



1 The pistillate catkins of this tree were figured in Bot. Mag. t. 8298 (1910), and show three-styled flowers, which never 

 occur in true P. nigra. Cf. p. 1796, note I. 



